1. Field of Invention
The invention relates to a color filter used for a liquid crystal display device or a solid-state image sensor, a production method of the color filter, and a solid-state image sensor using the color filter.
2. Description of the Related Art
As a method of producing a color filter used for a liquid crystal display device (LCD and the like) or a solid-state image sensor (CCD, CMOS and the like), a pigment dispersion method has been widely known.
The pigment dispersion method is a method of producing a color filter by a photolithographic method using a colored photosensitive composition in which a pigment is dispersed in a photosensitive composition. In this method, since the patterns are formed by the photolithographic method, the method exhibits a high accuracy in positioning and is suitable for producing a color filter having a large size and a high definition. When a color filter is produced by the pigment dispersion method, a photosensitive composition is applied on a glass substrate with a spin coater, a roll coater or the like to form a coated layer and the coated layer is pattern-exposed and developed to form colored pixels. This operation is performed repeatedly for the respective colors, whereby a color filter can be obtained.
As examples of the pigment dispersion method, a method using a negative photosensitive composition in which an alkali soluble resin is used in combination with a photopolymerizable monomer and a photopolymerization initiator is described (for example, see Japanese Patent Application Laid-Open (JP-A) Nos. 2-181704, 2-199403, 5-273411, and 7-140654).
In recent years, further high definition has been required for the color filter for solid-state image sensors in particular. However, in conventional pigment dispersion systems, it is difficult to further increase resolution, and there is a problem of unevenness of color which is generated due to the influence of coarse particles of pigment. Accordingly, the pigment dispersion system has not been suitable for the use of solid-state image sensors, in which, for example, minute patterns with a pixel size of from 1.5 μm square to 3.0 μm square are required.
In response, there has been proposed a technique in which a dye is used in place of a pigment (for example, see JP-A No. 6-75375). Furthermore, in recent years, a colored pattern with a thin film (for example, 1 μm or less in thickness) is required in the color filter used for a solid-state image sensor, in order to improve image quality which is achieved through good light-condensing and color separation properties. Accordingly, the dye concentration in a color filter must be increased in order to reduce the film thickness in view of obtaining sufficient color density.
In the production process of a color filter, a transparent protective film may be formed on a colored pattern having, for example, red (R), green (G) and blue (B). In general, the transparent protective film is formed in such a manner that a coating liquid for a protective film is coated on a colored pattern and then the protective film is subjected to heat treatment to be cured. For example, there is disclosed a technique, in which a thermosetting resin composition, which contains a polymer including an epoxy group-containing structural unit, an oxetanyl group-containing structural unit and an alkoxysilyl group-containing structural unit, and a polymer including an epoxy group-containing structural unit and an acrylate-based structural unit, is used, and the thermosetting resin composition is coated on the surface of a color filter at the side of the colored layer and is cured to form a protective film (for example, refer to JP-A No. 2008-83422).